by David Katzmaier March 12, 2010 6:45 AM PST
3D TVs are available now, but the new 3D technology inspires a Pandora's box of questions.
(Credit: 20th Century Fox)The recent flood of news about new 3D TVs, itself spurred by the hype surrounding the 3D release of "Avatar," has raised a few questions. This article, arranged in the tried-but-true manner of "Frequently Asked Questions," attempts to answer them.
When this FAQ was first published in January 2010 we polled the six major TV makers that announced new 3D models--LG, Panasonic, Samsung, Sony, Toshiba, and Vizio--to help with some answers. We also gleaned information from enthusiast sites like AVS forum and EngadgetHD. In the last couple of months more details have been announced, and we've had more in-depth conversations on the subject. You'll find many updates incorporated into the answers below, which represent our best current information on the subject.
This article is targeted toward people looking for an introduction to modern 3D TV technology. If you're an advanced reader just looking for the latest news your best bet is going straight to CNET's 3D TV resource guide. And if you have anything to add to this article, feel free to leave a comment or at least vote in the poll.
1. What is 3D TV?
3D TV is a generic term for a display technology that lets home viewers experience TV programs, movies, games, and other video content in a stereoscopic effect. It adds the illusion of a third dimension, depth, to current TV and HDTV display technology, which is typically limited to only height and width ("2D").
2. How can you get 3D from a 2D screen?
A 3D TV or theater screen showing 3D content displays two separate images of the same scene simultaneously, one intended for the viewer's right eye and one for the left eye. The two full-size images occupy the entire screen and appear intermixed with one another--objects in one image are often repeated or skewed slightly to the left (or right) of corresponding objects in the other--when viewed without the aid of special 3D glasses. When viewers don the glasses, they can perceive these two images as a single 3D image.
The system relies on a visual process called stereopsis. The eyes of an adult human lie about 2.5 inches apart, which lets each eye see objects from slightly different angles. The two images on a 3D TV screen present objects from two slightly different angles as well, and when those images combine in the viewer's mind with the aid of the glasses, the illusion of depth is created.
3. How is the new 3D TV technology different from older 3D?
Most people are familiar with the old anaglyph method, where a pair of glasses with lenses tinted red and cyan (or other colors) is used to combine two false-color images. The result seen by the viewer is discolored and usually lower-resolution than the new method.
The principal improvements afforded by new 3D TV technologies are full color and high resolution--reportedly full 1080p HD resolution for both eyes in the Blu-ray 3D, for example, and half that resolution in the DirecTV system. We expect DirecTV's 3D channels to look quite sharp despite lack of full 1080p resolution; see HDTV resolution explained for some reasons why.
A pair of LC shutter glasses
(Credit: Panasonic)
New 3D TVs require active liquid crystal shutter glasses, which work by very quickly blocking each eye in sequence (120 times per second systems like Panasonic's Full HD 3D). The glasses, in addition to the liquid-crystal lenses, contain electronics and batteries (typically good for 80 or more hours), that sync to the TV via an infrared or Bluetooth signal.
(Note: For the remainder of this article, any mention of "3D" refers to the new full-color, high-resolution version, not the old anaglyph variety.)
4. How is 3D TV different from 3D in the theater?
Many viewers have experienced newer 3D presentations, such as IMAX 3D, in movie theaters. Though the technologies differ somewhat--most theaters use passive polarized 3D glasses, for example--the main practical difference between 3D TV in the home and theatrical 3D is the size of the screen. In the home, the image is generally much smaller, occupying a lower percentage of viewers' fields of vision. Among TV makers we asked, only Panasonic recommend a closer seating distance (of 3x the screen height away--about 6.2 feet from a 50-inch screen) for a better experience; however, we suspect sitting closer or watching on a bigger screen will definitely help with any home 3D presentation. Smaller screens may also present other issues unique to 3D, such as a relatively narrow viewing distance range.
One advantage of 3D TV at home as opposed to the theater is user control. You can generally sit where you want relative to the screen at home, and some 3D compatible TVs provide some control over the 3D experience in addition to standard picture settings. Samsung's models, for example, allow you to adjust the "G axis," or the amount of 3D effect, to taste, comfort or to compensate for variations in eye spacing.
Since we at CNET haven't yet tested any 3D TVs thoroughly, we can't definitively speak to other differences between home and in-theater 3D yet.
5. Can everyone see 3D?
No. Between 5 percent and 10 percent of Americans suffer from stereo blindness, according to the College of Optometrists in Vision Development. They often have good depth perception--which relies on more than just stereopsis--but cannot perceive the depth dimension of 3D video presentations. Some stereo-blind viewers can watch 3D material with no problem as long as they wear glasses; it simply appears as 2D to them. Others may experience headaches, eye fatigue or other problems. (See also TV industry turns blind eye to non-3D viewers.)
6. I've heard 3D causes headaches. Is that true?
Most people watching 3D suffer no ill effects after a brief orientation period lasting a few seconds as the image "snaps" into place, but in others, 3D can cause disorientation or headaches after extended periods. Viewer comfort is a major concern of 3D content producers; too much of a 3D effect can become tiresome after a while, abrupt camera movement can be disorienting, and certain onscreen objects can appear blurry, for example. Creators of 3D movies for children also have to account for the fact that a child's eyes are closer together (about 2 inches) than an adult's.
7. Does everyone watching a 3D TV need to wear the glasses?
Yes. Every member of a family sitting around the 3D TV, for example, must wear the glasses to see the 3D effect. If they don't, the image on the screen will appear doubled, distorted, and, for most practical purposes, unwatchable. Currently, there's no technology that lets a single TV display both 2D and 3D content simultaneously without glasses.
People who wear normal prescription lenses already can experience the full effect--and generally suffer little or no discomfort--by wearing the 3D glasses too, which are designed to fit over an existing pair of glasses.
8. Do I need a new TV?
Yes. With one exception, none of the TV manufacturers we spoke with said that any of their current HDTVs can be upgraded to support the new 3D formats used by Blu-ray, DirecTV and others. One reason we've been given is that the TV must be able to accept a higher-bandwidth signal (technically 120Hz) to display Blu-ray 3D, and older TVs can typically only accept relatively lower-bandwidth (60Hz or less) signals. That's potentially confusing because many non-3D LCDs have 120Hz and 240Hz refresh rates, and manufacturer marketing also mentions "600Hz" plasmas. Regardless of the "Hz" spec, these non-3D models can only handle a source that outputs at 60Hz or less via HDMI--the "conversion" to a higher rate, if applicable, occurs inside the TV itself.
Another reason is that 3D requires different video processing and additional hardware, including some way to send the necessary Infrared or Bluetooth signal to the 3D glasses. We're not ruling our the possibility of third-party add-ons overcoming these limitations, but as of now there's no way to convert any 2D TV to be compatible with the new 3D TV formats. more...
